1. Technical Field of the Invention
The present invention relates to a thermally insulated synthetic resin container and a thermally insulated synthetic resin lid which are used for thermos bottles, cooler boxes, ice boxes, thermally insulated cups, thermally insulated lunch boxes and such. More specifically, the present invention relates to a thermally insulated synthetic resin container and a thermally insulated synthetic resin lid which aim to secure the thermally insulating layer body or the thermally insulating layer body of the lid, possessing a double wall structure which encloses a thermally insulating layer filled with gas having low thermal conductivity, within the open layer of the inner and outer containers or the upper and lower surface walls of the lid, and which aim to prevent the rattling of the thermally insulating layer and the thermally insulating layer of the lid.
This application is based on patent application No. Hei 8-309768 filed in Japan; the content of which is incorporated herein by reference.
2. Description of the Related Art
A thermally insulated container, having an inner container and an outer container which are formed with synthetic resin material, with this inner container placed within the outer container while providing a space portion in between, and filling inside this space portion, at least one type of gas from among xenon, krypton, and argon, has been proposed heretofore as a thermally insulated synthetic resin container.
This type of thermally insulated synthetic resin container has provided a metal plating film on the outer surface of the inner container and the inner surface of the outer container in order to improve the gas barrier properties.
As for the forming of this type of metal plating film, in the case where resin which allows the direct application of the metal plating is used, there is a need to provide masking on the inner surface of the inner container and the outer surface of the outer container as well as the joining surface of the inner and outer containers in order to prevent the adhesion of the metal plating. This type of masking requires high precision in positioning and such, and the cost of masking, as well as that of electroplating and such performed after masking, are high. In addition, the masking process produced containers which are defective in appearance due to the metal plating film adhering to locations where the masking coating was missing or where the masking coating was accidentally stripped, and also required safety management of the masking coating as well as management to ensure the secure adhesion of the masking coating to the resin. Consequently, the masking process has an impact on the cost, the freedom of design, and durability of the container.
In the case where resin which does not allow the direct application of the metal plating is used, there is a need for an initial production process which involves the application of ABS coating or such in order to form the metal plating film. And this additional process is one of the main cause of the increase in cost.
Additionally, when strengthening the adherence of the metal plating film, there is a disadvantage of having the number of usable resins being limited and sacrificing such properties as rigidity and alkali resistance of the synthetic resin.
In addition, the formation of the metal plating film makes impossible the recovery of the synthetic resin when recycling during the manufacturing process or the disposing process, thereby increasing the cost of the container in the long run.
Furthermore, there are problems with the thermally insulated containers when synthetic resin materials having good gas barrier properties are used. Most of those resins have good hygroscopic properties, and when those resins absorb moisture, then their gas barrier properties deteriorates. Consequently, problems such as not being able to obtain desired properties exist. In addition, there are such disadvantages where the mechanical strength is lacking in certain types of resins or where the mechanical strength of a synthetic resin having good hygroscopic properties decreases due to the absorption of moisture.